The invention concerns a balloon catheter.
Angioplasty of a narrowing in a vessel or a vessel stenosis caused by arteriosclerosis using a balloon catheter leads to excessive multiplication of cells in the walls of the vessel in 30 to 50% of all treated patients which contributes to a restenosis of the vessel. The angioplasty triggers excessive cell production in the tissue of the cell wall as well as migration of smooth muscle cells of the tissue into the innermost layer of the artery. This process leads to so-called intimal hyperplasia which once more narrows the vessel.
There are other usable angioplasty methods for opening closed vessels via a laser or with atherectomy catheters for removing the stenostic material. These methods, as is the case with the balloon catheter, lead however to intimal hyperplasia.
The use of radioactive radiation to prevent excessive cell growth is known in the art for treatment of tumors or of intimal hyperplasia.
One possibility is to utilize radioactive radiation for the prevention of intimal hyperplasia through the temporary introduction of radioactive instruments or apparatus into the arteries or into a balloon catheter (U.S. Pat. No. 5,199,939 or U.S. Pat. No. 5,213,561). These methods have the disadvantage that the walls of the vessel are not evenly irradiated (U.S. Pat. No. 5,199,939) due to a poor centering of a thin radioactive wire or catheter or that there is no direct contact between the radioactive element and the walls of the vessel (U.S. Pat. No. 5,213,561 and EP 0 633 041 A1) so that large radiation doses are necessary to prevent the restenosis.
Pure beta-emitters are e.g. mainly effective at short ranges in the tissue and the effect of the radiation decreases significantly with increasing distance from the source location. High energy gamma-radiation emitted e.g. from the radioactive nuclide Iridium-192 (U.S. Pat. No. 5,213,561)) penetrates the radioactive element guiding catheter without large dose losses. However, the radiation dose is not completely absorbed in the walls of the artery, rather penetrates into the body of the patient. All catheters having radioactive elements must be sufficiently flexible and soft in consistency in order to avoid injuring the vessels.
One possibility of directly irradiating the walls of the vessel with low doses is the utilization of radioactive stents or vessel implants (EP patent 04 33 011 A1 and DE patent 43 15 002 C1). The implantation of stents can, however, lead to blood clots and to the sealing of the vessels due to the introduction of foreign materials into the human arteries which could result in destruction of tissue in the organ being treated. In addition, conventional clinically used stents can cause foreign allergic reactions resulting in the diffusion of infective cells into the walls of the vessel. In addition, for purposes of minimizing the radioactive dose on the entire organism, a rapid short-term radiative treatment is preferred rather than a long-term radiation treatment using a radioactive vessel implant.
The invention avoids the above-mentioned disadvantages. The invention concerns a balloon catheter, a method for its production and a partially manufactured product (balloon catheter having metallic coating) which can be transformed into a balloon catheter in accordance with the invention through radioactive transformation.